Pneumatic brush holder



- Dec. 1 1925. 1.563.397

R. E. RAMBO PNEUMATIC BRUSH HOLDER Filed April 1924 Fil.

Fig.2. a a9 wmuzsszs; INVENTOR Rawdon Evans Rambo.

ma a, M

ATTORNEY Patented Dec. 1, 1925.

ATENT OFFICE.

BAWDON EVANS RAMBO, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR T0 WESTING-HOUSE ELECTRIC & MANUFACTURING COMIANY, A. CORPORATION OF PENNSYL-VANIA.

PNEUMATIC BRUSH HOLDER.

5! '0 all whom it may concern:

Be it known that I, RAWDON Evans R anso, a citizen of the United States,and a resident of \Vilkinsburg, in the county of Allegheny and State ofPennsylvania, have invented a new and useful Improvement in PneumaticBrush Holders, of which the following is a specification.

My invention relates to brush holders for dynamo-electric machines andit has special reference to brush holders of the type in which the brushis held in contact with the commutator cylinder by pneumatic pressure.

In devices of this type in the prior art, certain inherent defects havebeen found which are overcome by my invention. It has heretofore beenusual in pneumatic brush holders to apply the pressure to the brush bymeans of a plunger engaging the brush and operated by pneumatic pressureapplied to it.

Brush holders of the type just mentioned have been found unsatisfactory,because they do not maintain the brush in constant, even contact withthe commutator cylinder during the operation of the machine.Irregularities in surface of the commutator cylinder resulted in causingthe brush to vibrate or chatter, as the commutator rotated. and theinertia of the piston increased the time taken by the brush to return tothe commutator surface after passing over a rough spot thereon. As aconsequence, cracking and splintering of the brush frequently resultedand the commutation was not as good as it should be.

One of the objects of my invention is to provide a brush holder whereinthe brush may be firmly held against the comn'iutator cylinder by thedirect application of pneumatic pressure to the brush.

Another object is to provide a brush holder of the above-mentionedcharacter which will not require the connection of leads to the brushproper. v

Another object is to provide a brush holder in which the application ofpressure to the brush will be such that, although the brush will bemaintained in good contact with the commutator cylinder and will beautomatically adjusted to the irregularities of the surface thereof, itwill not be splintered or cracked or otherwise damaged by themaintenance of the proper degree of pressure.

Another object is to provide a brush holder of the pneumatic type inwhich the brush may be readily installed or removed, and to which it maybe closely connected and finely adjusted.

Another object is to provide a brush holder which shall be of few partsof simple and cheap construction, shall have a high degree ofefficiency, and shall be capable of maintaining a positive, but elastic,pressure upon the brush without damage thereto, and which may have otheradvantages and results more specifically hereinafter set forth.

My invention consists in the particular organization, combination, andarrangement of parts hereinafter described and ,more specifically setout in the appended claims.

In the accompanyingdrawing, in which like numerals of reference indicatecorresponding parts,

Figure l is a view in side elevation of an assembly of four of myimproved brush holders, operably related to a commutator cylinder, onlya fragmentary portion of which is shown. i

Fig. 2 is a vertical cross-sectional view taken on the line IIII of Fig.1, showing my improved brush holder mounted on a portion of a supportingyoke, and

Fig. 3 is a vertical cross-sectional view of a modified form of myimproved brush holder, showing a brush holding chamber of uniform size.

In Fig. 1 is shown a sectional view of a commutator cylinder 1, inoperative relation to which an assembly of pneumatic brush holders 2 ismounted. In the device as shown in Fig. brush holders. Each brush holderiscarried upon a supporting arm or yoke 3,,whioh provided with anenlarged end 4 having an inset or incut' portion 5 and'an opening 6therein, the latter being adapted to receive a stud bolt 7 which engagesa threaded aper-' ture 8 in a lug or' footportion 9 of the brush holderbody portion 10.

The brush holder box'or body may be of any desired outward formation,but must be provided with an interior chamber 11 of 1, there areassembled ,4

such size and shape as to operably receive and retain the brush 11a,which may be of any usual or desired size and shape.

In the form of brush holder shown in Fig. 2, one side of the brushholder box, or more especially the chamber 11 therein, is of uniformshape, in this instance a straight surface, while the upper portion ofthe opposite side is provided with an incut channel or enlarged portion12. This channel or enlarged portion 12 extends from the top of thebrush holder box to approximately its middle point and is provided inorder to permit eonvenient. removal of the brush 11 from the brushholder box, when because of breakage or other reason, such removal isdesired. The brush 11 is provided, near its upper end, adjacent to theenlargement or slot 12, with a notched or incut portion 18 which is soarranged as to receive a hook or other implement that can convenientlybe inserted into the brush holder box, along the channel 12 and into thenotch 13, in order to eifect the convenient removal of the brush.

The lower portion of the front face of the brush holder chamber isprovided with a series of laterally disposed substantially parallelchannel portionsli r, spaced apart from each other, which act as aseries of battles to control the flowbt air in that portion 01 thechamber when the brush holder is under the intended operating pressure.There is also, in the lower portion of the rear taco of the brush holderchamber, a substantially vertically disposed. channel portion 15, at theends of which there are provided outlets or vents 16 and 17,respectively, which communicate with the atmosphere.

The brush holder box or body is provided at its top with laterallyextending lugs or flanges 18 and 19 provided with threaded openings 20and 21. Seated upon the top flanged end of the brush holder box 1s a capor cover 22- which is also provided with flanges or lugs 23 and 24.-similar to the lugs 20 and 21. of the main body portion of the brushholder box. The lug or flange portions 23' and 24: of the cap or cover22 are provided with openings 25 and 26 Which. register with theopenings 20 and 21 in the flanged portion of the brush holder box.

The cap 22 is held in operative relation to the brush holder box,closing the upper end thereof, and making an air-tight joint therewith,by means of stud bolts 27 and 28, threaded into the'open-ings 20 and 21in the brush holder box and passing through the openings 25 and 26 inthe cap 22. It will be understood that although I show means of holdingthe cap in operative position on the brush holder box, any othersuitable fastening means may be employed.

The cap22 is provided with a substantially centrally positioned tubularportion 29 having an inlet or opening 30 which ex.-

tends through the cap 22 and communicates with an opening 31 in the baseof the top or cover 22, so that pneumatic pressure may be applied to thechamber 11 and to the brush 11a therein, when the opening 30 isconnected to one or more pipes 32, supplying pressure from a source nothere shown.

I assemble my brush holder by mounting it upon the supporting yoke 3,inserting the brush 11a therein, properly closing the top by the cap 22,and connecting the brush holder chamber with a source or? pneumaticpressure through the pipes 32. The operation of the device is asfollows.

Pressure, approximately three pounds to the square inch, is admitted tothe chamber 11, and the brush. receiving this pressure upon its tor-wardface, is forced into close and tight contact with the rear :l ace of thebrush holder chamber. \Vhen this takes place, such air as may be betweenthe brush and the rear face of the brush holder chamber, is forced intothe channel 15 and out to the atmosphere through the vents 16 and .17. Ithereby utilize the pneumatic pressure to form a good contact betweenthe brush and the brush holder box, and by this means I am enabled toeliminate the use of leads connected to the brush.

lllaviue adjusted the brush to the tftllllllllltator cylinder, thedesired pneumatic pressure is applied to the brush head and the brush isthus held in firm, close but elastic contact with the commutatorcylinder so that as the cylinder rotates it will :uitomatically adjustitself to irregularities oi the connnutator surface. .The air cushionformed in the upper end of the brush holder chamber permits a resilientaction oi: the brush upon the commutator cylinder so that it will.maintain a perfect contact while at the same time it will not be subjectto the chattering, cracking, splintering or other disintegrzu tionswhich are encountered in pneumatic brush holders of the type applyingpressure to the brush by means of a. plunger. Not only is this true, butI am enabled to zuaiu tain a. perfect coinact by my device with the useof pressure of approximately three pounds per square inch. aboveatinospl'icric pressure wl'icreas in the plunger type o t pneumaticbrush. l'lOlClClfS where the PlQSStU'C.

is applied to the brush end by a plunger 01 comparatively smallcross'sectional area, the pressure of: this plunger against the brushfrequently exceeds 25 or 30 pounds per square inch and. results indefective opera tion.

Vhen the brush wears and moves downwardly under pressure, thebatlles orehannels 14; operate to. trap air which. may pass between the front faceof the brush and the face of the front portion. of the brush holderchamber and prevent or curtail the leakage of the air from the brush,holder chamber,

while at the same time exerting a pressure tending to hold the brushfirmly in contact with the rear face of the brush holder chamber inorder to conduct the collected current from the brush.

lVhen the brush has worn to such length that the top end is below thevent 17, the whistling or noise produced by the exhausting air throughthis vent serves as a signal to indicate the need tor renewal of thebrush. This may be accomplished, as before stated, by the removal ot thecap .22 and the lifting out of the brush by means of a hook or otherimplement which can be made to engage the slot 13 in the upper end ofthe brush. A new brush may be placed in the holder and the cap replaced.

In Fig. 3 a brush 11a operates in a chamber 2325 in substantially thesame manner as that explained in connection with the type shown in Fig.2, except that there is no enlargement oi the upper portion of one sideof the brush holder chamber. In some respects this is my preferred formof construction, and I believe a better contact may sometimes beobtained between the brush and the brush holder in this type of chamberand a greater o'tliciency oil the brush thereby secured.

I prefer to construct my brush holder box or? brass, although anysuitable metal or material may be used which will provide a goodcollector of current from the brush and 21' sliding relation between thebrush and the brush holder box with the minimum amount of Friction.

It will be seen, therefore, that my iniproved. brush holder is otextremely simple constriu-tion. of tow parts and ot a high degree o'teltiriency: it ctl'ects the collection and distriluiti on of the currentwithout leads connected to the brush; it automatically provides a signalwhen there is need o't renewal of the brush: it results in theelimination of the detects hereto'tore known in ymeumatic brush holdersand prevents the chattering, shattering, splintering and otherdisintegra tion of the brushes; it results in long life and otlicioncyot the brush itself, and it has other advantages not specifically hereinset Forth.

Although l have shown but two embodiments ol my invention, yet I do notwish to be limited thereby except as the state of the art and theappended claims may require, for it is obvious that certainmodifications,

reorganizations and combinations of parts may be made without departingfrom the spirit and scope of my invention.

I claim as my invention:

1. A current-collecting device comprising a brush holder having abrush-holding pressure chamber, means for applying fluid pressure to thehead of said chamber, and a brush slidably fitting in said chamber andoperating as a piston actuated by said fluid pressure, said devicecomln'ising transversely extending fluid pockets between said brush andthe side wall of said chamber for hunting the escape of fluid.

A current-collecting device comprising a brush holder having abrush-holding pressure chamber, means for applying fluid pres sure tothe head of said chamber, a brush slid-ably fitting in said chamber andoperating as a piston actuated by said fluid pres sure, and means "forcausing the fluid pressure to be greater on one side face of the brushthan the other for holding said brush in firm contact with one side wallof the chamber.

3. A. current-collecting device comprising a brush holder having abrush-holding pressure chan'iber. means for applying fluid pres sure tothe head of said chamber, a brush slidably fitting in said chamber andoperating as a piston actuated by said fluid pres sure, said brushholder having transversely extending fluid pockets between said brushand one side wall of said chamber, and means 'for preventing theaccumulation of luid between said brush and the opposite side wall ofthe chamber.

4. A crwrenhcollecting device comprising a brush holder having abrush-holding pressure chamber, means for applying fluid pres sure tothe head of said chamber, and a brush slidably fitting in said ehan'iberand operating as a piston actuated by said [laid pressure, said devicebeing provided with fluid-(scape channels between said brush and oneside wall of: the chamber.

The combination with a brush holder, ot a brush mounted therein, saidbrush having a notch near the top 01": a side face there oi. and saidholder having an enlarged ehan ncl adjacent said notch "for Facilitatingthe removal ol? the brush.

l n testimony whereof. I have hereunto subscribed my name this 28th dayot March 1924.

RAVJDON EVANS RAMBO.

